The present application is directed to fluid ejectors, and more particularly, to fluid ejectors using piezoelectric actuation, and methods to make the same. Micromachined fluid ejectors, such as ink jet printheads, using either electrostatic or piezoelectric actuation have been discussed. When electrostatic actuation is employed, the fluid ejectors are fabricated using standard silicon micromachining processes. Because the energy density of electrostatic actuators is very small, the required driving voltage is quite high (e.g., commonly 50V or more). Use of electrostatic actuation also makes the ejectors vulnerable to damage caused by the snap-down operation of the active diaphragm.
Fluid ejectors employing piezoelectric actuators have also been considered. Several advantages exist in the use of piezoelectric actuation, including lower driving voltages and elimination of device failure occurring due to snap-down of an active diaphragm. Bulk piezoelectric actuation systems commonly require larger driving voltages than ejectors which employ piezoelectric thin films since, for example, the distance between the electrodes is larger in the bulk piezoelectric actuators. In either case, either type of piezoelectric actuator based fluid ejector requires lower driving voltages than electrostatic based ejectors. While lower driving voltages are expected for thin film piezoelectric actuators, there are several challenges in making operable piezoelectric thin film based fluid ejectors, especially for micromachined fluid ejectors. Particularly, sufficient energy must be developed by the piezoelectric material, and that energy must be effectively transferred to the fluid for consistent controllable drop ejection.